1. Technical Field
The present invention relates in general to cooling systems for electronic devices and, in particular, to cooling fans. More particularly, the present invention relates to an integrated fan assembly that utilizes a embedded fan controller.
2. Description of the Related Art
Integrated circuits and other electrical devices generally have rated operating temperature ranges. Within these operating ranges, the devices behave according to specified requirements. Outside of the rated operating range, the response characteristics of the circuits and devices can vary from the specified requirements. At elevated temperatures, it is known for integrated circuits and other electrical devices to fail or burn out or otherwise become defective. Accordingly, it is desirable to maintain circuits and devices within their rated operating temperature ranges.
In a computer system, continued operation of an electronic device leads to the generation of heat. In some instances, albeit rare, ambient air is sufficient to provide cooling to maintain the circuit or device within the desired operating temperature range. However, some circuits or components generate enough heat to require affirmative cooling from a cooling fan. Typically, computers have included a cooling fan inside the computer housing to prevent overheating caused by the normal operation of the computer. Also, it not uncommon for a computer system, such as a server system, to utilize more than one cooling fan to maintain a specified operating temperature.
Computer systems must monitor their cooling fans to verify that the fans are powered on and rotating at a predetermined speed to maintain a desired thermal condition that precludes accelerated failures of electronic devices utilized in the computer systems. Typically, each cooling fan generates a xe2x80x9cfeedbackxe2x80x9d signal that provides information, such as rotational speed. The feedback signal is generally a xe2x80x9ctachxe2x80x9d signal that is essentially a pulse train where each pulse represents a complete revolution of a fan blade. A monitoring processor, typically a system processor, receives this feedback signal at a fan sense pin.
The speed at which a cooling fan is operated is generally a function of the heat dissipation and acoustical noise requirements of the system in which it is utilized. For example, a fan operating at a high speed typically generates a higher noise level than a fan operating at a lower speed. The different cooling and acoustic noise requirements result in a different fan speed operation requirements. Thus, a manufacturer must customize a cooling system for each different application. This, in turn, results in the manufacturer utilizing a different xe2x80x9ccustomxe2x80x9d fan for each separate application or product, increasing the manufacturer""s inventory and cost.
Accordingly, what is needed in the art is an improved cooling fan that mitigates the limitations discussed above. More particularly, what is needed in the art is a single cooling fan that can be operated at different speeds to accommodate the different environmental requirements of disparate systems or applications.
It is therefore an object of the invention to provide an improved cooling fan.
It is another object of the invention to provide an integrated fan assembly with an embedded fan controller.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a fan controller for use with a variable speed fan is disclosed. The fan controller includes a processor coupled to a communication circuit that, in an advantageous embodiment, includes a universal asynchronous receiver transmitter (UART). The communication circuit allows an external controller to monitor and establish a desired speed setting of the variable speed fan. The fan controller also includes a memory device, such as an electrically erasable programmable read only memory (EEPROM), coupled to the processor, that contains the desired speed setting of the variable speed fan. The fan controller further includes a feedback circuit, coupled to the processor, that receives a feedback signal indicative of the variable speed fan operation and a fan driver circuit, coupled to the processor, that provides a driving signal to control a speed of the variable speed fan.
The fan controller along with the associated variable speed fan constitutes a xe2x80x9cphase locked loopxe2x80x9d system where the variable fan speed is constantly monitored and adjusted accordingly to meet the predetermined speed requirements of the overall system where it is employed. The predetermined, i.e., desired, speed is contained in the memory device and the fan motor currents are adjusted until the desired speed is obtained. The fan controller communicates with and is typically under the control of a supervisory processor of the host machine via a bidirectional bus, allowing the fan controller to notify the supervisory processor of any existing problems. The present invention permits the utilization of a single fan assembly for use with disparate systems having different cooling requirements. The speed settings for the different cooling environments can be xe2x80x9cflashedxe2x80x9d into the memory device of the fan controller, thus allowing a single fan assembly to be inventoried reducing overall costs in manufacturing and operation.
The foregoing description has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject matter of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.